Tamping machines are used to repair and correct the ballast around and beneath railroad ties so that the roadbed can uniformly support the passage of railroad trains over it. Tamping machines are designed to move along the roadbed and at each tie to force at least eight tamping blades into the ballast, one blade on each side of each tie on each side of each rail. The tamping blades are then vibrated and moved toward the tie in unison to compact the ballast under the tie and provide a firm formation around and beneath the tie. The railroad bed in turn provides a solid foundation for the heavy loads encountered as a train passes thereover.
A primary difficulty is that the typical ballast materials are highly abrasive, e.g. sand, slag, gravel and cinders. The leading edges of the tamping blades wear away rapidly, and the tamping blades must be replaced or the leading edges of the tamping blades rebuilt. See e.g. U.S. Pat. No. 3,826,025. Typically, the edges of the tamping blades are faced with a high chromium-steel braze to provide added wear resistance. Yet, even with chromium-steel facing, a noraml run is only 4 to 6 miles of roadbed before the edges of the tamping blades are worn to the point where replacement is necessary for efficient operation.
The life of the tamping blades have been substantially increased by providing a tungsten carbid insert in the leading edge of the tamping blade. Such a tamping blade is described in U.S. Pat. No. 3,793,960, issued Feb. 26, 1974. The carbide insert is nested and brazed into a groove formed in the leading edge of the blade. The carbide insert is of sufficient bulk and is adequately supported by the surrounding groove to avoid chipping, cracking and spalling of the insert under the heavy impact loading to which the leading edge of the blade is exposed.
This construction substantially increases the life of the tamping blade; such blades are, however, still limited in their useful life. Because of the necessity for the groove-nested insert, the blade does not have a wear-resistant facing across the entire leading edge. Moreover, such blades have no wear-resistant facing to protect the blade during lateral movement through the ballast. As a result, such blades wear rapidly and eventually "wash-out" at the edges of the groove supporting the insert, thereby requiring replacement of the entire tamping blade.
The present invention overcomes these difficulties and disadvantages, and provides a tamping blade with a substantially prolonged useful life. A carbide insert provides a hard wear-resistant facing across the entire leading edge of the tamping blade and the lateral facing of the blade, while supporting the insert so as not to crack, spall or chip on impact loading.